It is conventionally known that when a substance having a structure in which graphene sheets are laminated, such as graphite, is oxidized, the graphene sheets constituting the substance can be peeled off sheet by sheet. As such, the technology for producing graphene sheets having a thickness in the atomic scale is expected as a core technology in the field of nanotechnology. For example, when graphitic graphene is oxidized, graphene oxide is obtained. Since this graphene oxide peels off into single sheets in water, there has been suggested a method of obtaining a graphene thin film by laminating the material on a substrate to produce a graphene oxide film, and then reducing the thin film (Non-Patent Literatures 1 to 3).